This invention pertains to the bonding of optical fibers along their lengths to form a self organized array, and to methods of making such assemblies into high density optical connectors and optical fanouts.
The bonding of optical fibers along their lengths to form hexagonal and cubic ordered arrays using organic adhesives has been demonstrated with less than optimal results. Alternatively, hexagonal and cubic ordered arrays of individual fibers have been heated, melted and drawn into fused arrays as well. However, in the case of fused arrays, separating the fibers into reliable individual elements that can be interconnected with standard telecommunications grade fiber is problematic. In the field of high density optical interconnects, what is needed is an ordered array of telecommunications grade fiber permanently bonded in a dense array of high positional tolerance on one end, and a xe2x80x9cfan-outxe2x80x9d of individual fibers (or ribbons of fibers) on the other.
One approach to realize this configuration, is to use an organic adhesive, such as epoxy, to bond the fiber array along the lengths of the individual fibers. As a convenient and low cost solution, epoxies have many additional advantages, not the least of which is their low viscosity (important for high dimensional precision, i.e. thin bond line), strength, toughness and ease of application. However, irrespective of cure technique (UV, thermal, etc.), epoxies have modest glass transition temperatures (Tg) in which their mechanical properties are better described as visco-fluidic rather than solid. Unfortunately, the transition between fluidic and solid is more or less a continuum in which the onset of undesirable visco-fluidic characteristics of the epoxy can occur at temperatures significantly below that of the Tg. This in turn can lead to bonded parts of poor dimensional stability at environmental temperatures significantly below the Tg of the adhesive.
In addition to the issue of dimensional instability, the high thermal coefficients of expansion (TCE) of epoxies, in particular for temperatures approaching the Tg (typically xcx9c125xc2x0 C.) whereby the TCE in general increases threefold, can cause mechanical reliability concerns of the optical fiber itself.
For these reasons of performance and mechanical reliability, the telecommunications industry has shown reluctance in fielding systems which make use of organic adhesives in xe2x80x9cmission criticalxe2x80x9d components.
There is a need to produce a bonded fiber array with acceptable performance and mechanical reliability for use in the telecommunications industry.
The one respect, the invention comprises a fiber optic assembly comprising a plurality of optical fibers. An inorganic adhesive having a glass transition temperature of at least about 150xc2x0 C. bonds each fiber to at least one other fiber along a bondline.
In another respect, the inorganic adhesive preferably comprises a sol-gel having a glass transition temperature of at least about 150xc2x0 C. and the bondlines between adjacent optical fibers in the array are less than about 200 nm in thickness.
In yet another respect, the invention comprises a fiber optic assembly comprising a plurality of optical fibers bonded together along a plurality of bondlines by an inorganic adhesive. The bondlines correspond to lines of contact between each of the optical fibers. The inorganic adhesive is preferably formed from a colloidal suspension of sodium silicate.